pixmapmanipulator: add cropping possibility

contact images provided by OSX Contact app are all squared.
There was no handling of other images resolution, then drawing was
all wrong for images with width != height

Change-Id: Ib888d6a0d9c609f8090058d7d062a438f48fe35f
Tuleap: #530
diff --git a/src/delegates/ImageManipulationDelegate.h b/src/delegates/ImageManipulationDelegate.h
index 141329a..776df95 100644
--- a/src/delegates/ImageManipulationDelegate.h
+++ b/src/delegates/ImageManipulationDelegate.h
@@ -55,6 +55,11 @@
         //Helper
         QPixmap drawDefaultUserPixmap(const QSize& size, bool displayPresence, bool isPresent);
         CGImageRef resizeCGImage(CGImageRef image, const QSize& size);
+
+        /**
+         * Return a version of size destSize centered of the bigger photo
+         */
+        QPixmap crop(QPixmap& photo, const QSize& destSize);
     };
 
 } // namespace Interfaces